This invention pertains to the field of control systems for scale model railroad layouts, and specifically to expanding control capabilities, beyond locomotive speed and direction, for conventionally powered model railroad layouts by using mixed power control methods.
The advent of Command Control technologies has led to increased enjoyment and capabilities for model railroaders and their operations of model railroad layouts. All control systems are connected to the layout tracks and are at least capable of controlling the speed and direction of a single locomotive on the train tracks. Conventional AC or DC power control systems adjust locomotive speed simply by the varying amplitude of the track voltage. Direction is controlled by polarity or other encoded track voltage change such as voltage dropouts or higher voltage pulses. Any improvements beyond this basic capability to control other model operating aspects such as lights, sound generators, smoke generators, animation, etc., are considered expanded control function capabilities.
Since the early Carrier Control systems of the 1970's and up to the latest Digital Command Control (DCC) technologies, one key capability of all the technologies is the same. This is the ability to control multiple independently addressed locomotives in the same electrical section of model railroad tracks.
All the technologies that communicate these addressed commands to a particular receiver, or decoder, in the locomotive by electrical conduction via the rails employ some variant of encoded time-varying voltage waveforms, and are termed Command Control systems. In addition, some prior art Command Control systems have been developed that control decoders via a Radio Frequency link or an Infra-Red data link, with energy supplied via the track or batteries, and these variants can be also considered to behave in a similar manner and scope to the systems discussed herein.
As technology and miniaturization have improved, the encoding methods, features and capabilities have been upgraded, but the net effect is still fundamentally that of allowing multiple simultaneous train control capability in at least a single track-section. This is a capability that no earlier conventional AC or DC power control system possessed and is why these older single-control per track conventional control systems have been surpassed by Command Control methods.
The earliest GE “Astrac” system was one of the first analog “frequency modulated” waveform train Carrier Control systems, followed by the control methods employed by Lahti in U.S. Pat. No. 4,341,982. In the early 1980's the Hornby “Zero-One” system, as taught by Palmer in U.S. Pat. No. 4,335,381, provided one of the first examples of a modern Digital Command Control, or DCC, system with digital command encoding methods that are direct precursors of the latest addressable message-based Digital Command Control art. In addition, the Marklin “AC Digital” or Trinary DCC system as an example of a bipolar square-wave digital control signal was also introduced in the mid-1980's, and is taught by Hanschke in U.S. Pat. No. 4,572,996. Bipolar square-wave digital control signals have become widely used because they are easy to create and decode, and the signal also is also the power source to operate the layout.
The freedom to operate multiple receiver, or decoder, equipped locomotives then raises a further question of interchange of and coupling of different technology locomotives on and between layouts equipped with; Carrier Control, Command Control or Digital Command Control and other conventional layouts and locomotives without these new capabilities. These different modes of operations using different control technologies are not inherently compatible. The coupling together of multiple-unit locomotives is termed a “lash-up”, or consisting. American prototype railroad practices using diesel locomotives commonly consist two or more locomotives to haul long coal train or other bulk loads, so modelers have requirement to do this on a model railroad to maintain realism.
The problem of interchange of DCC decoder equipped locomotives onto conventional DC power control systems, and also the converse situation of operating DC controlled locomotives on DCC systems, was also addressed by the public domain National Model Railroad Association (NMRA) DCC Standards and RP's, introduced in the early 1990's, that are well known and widely used internationally and that are based on the earlier Marklin “DC Digital” system developed by Lenz Electronik GmbH. This method also uses a bipolar square-wave digital signal that encodes digital command control data by timed changes of track voltage.
In particular, the NMRA DCC technology teaches an automatic, or selectable, Power Source Conversion, or Mode Conversion, option that permits the decoder to detect that it is connected to and then operate on a conventional DC power control system, or other control method, rather than a compatible NMRA DCC encoded control system. This is often referred to as “automatic Analog Mode conversion” allowed by the NMRA [using the optional Power Source Conversion ID codes defined in CV12 of the well known NMRA Recommended Practice RP-9.2.2 and its associated Appendix B] and enabled by the state of the decoder's CV29 bit 2, as defined in the NMRA RP-9.2.2. This was based on an original German patent filed by Lenz and that has since elapsed.
Accordingly, when the decoder (or receiver) detects the tracks being driven by a conventional DC power control system instead of a NMRA DCC signal it changes control strategy and modulates the H-bridge motor drive circuit so as to supply the DC input power to the motor. The speed of the motor is then controlled by the amount of conventional DC voltage supplied, and can also be modified by decoder actions such as simulated momentum. The track polarity of the DC control signal determines the locomotive direction, so the decoder interprets this and drives the motor H-bridge direction accordingly.
The well known NMRA prior art uses the term Power Source or “mode-conversion” to describe the action of a decoder, or other control device, that detects a change of the nature of the track control system it is connected to then allow a change of control action to operate under the influence of the newly detected type of track control system.
Ireland in U.S. Pat. No. 6,513,763 teaches a new method for allowing a digital or Command Control decoder equipped locomotive to operate with correct speed and direction matching when operated on a conventional AC or DC power control system alongside conventional locomotives with no decoders installed. This allows flexibility by allowing the interoperation of a mix of digital and non-digital equipped locomotives on different layout control schemes.
However, while Ireland U.S. Pat. No. 6,513,763 allows for accurate speed and direction control of digital locomotives running on conventional power layouts (i.e. variable analog DC or AC voltage controlled layouts), the digital function outputs used to control lamps, couplers and other items such as sound generators are not fully controllable on these conventional layouts.
Severson et. al. in U.S. Pat. No. 5,896,017 teaches the use of a sequence of DC track polarity reversals and/or High Voltage track pulses to allow limited control of functions on a locomotive to be effected using a conventional DC power control system. For, example when the user briefly and rapidly reverses the track direction control (or polarity) a defined number of times a whistle sound, or a lamp etc., can be actuated. This method is effectively an extension of the Onboard State Generator concept introduced by Severson in U.S. Pat. No. 4,914,431.
While Severson U.S. Pat. No. 5,896,017 teaches a control extension for a conventional DC power control system that requires no new hardware, it has a number of severe drawbacks and constraints that make usage tedious and cumbersome. The use of a DPDT manual switch to create the necessary track polarity reversals for control requires the user to accurately manipulate this DPDT switch with repeatable and recognizable patterns. Thus, if a user fails to properly execute any one of the sequences of multiple switch actuations, then the desired action will not be encoded properly, and this may not be apparent to the user until the expected action does not correctly occur. In addition, there is a likelihood of fatigue or even repetitive stress injury if many actuations are required to realistically operate the model railroad over a period.
For this control method to be effective in expanding the control capabilities of a DC power control system the user now has to remember a complex set of switch actuation sequences, and may have to explain these to a guest user or operator or locomotive “engineer”.
If non-decoder equipped conventional DC locomotives are consisted with decoder equipped locomotives controlled by Severson's polarity reversal technique there is a severe problem that these controlling polarity reversals will cause these conventional locomotives to briefly and undesirably change direction. This makes consisting in this manner problematic, and limits the scope and flexibility of this control method. Polarity reversal encodings that are compatible with human hand movements are necessarily slow, and in the range of about 1 encoding polarity reversal per second and so the control rate or bandwidth of this technique is low. This is especially true when contrasted with a Command Control method that typically can provide hundreds or more control encodings per second.
To overcome some of these problems it is possible to place a polarity reversing control unit in series with the DC power control system that uses, for example an interposing DPDT relay driven by control logic to provide accurate, complex and repeatable polarity reversals. This allows the user to actuate one of a number of control switches on this polarity reversing control unit that then encodes a unique control action. An example this automation is a “Sidekick” auxiliary controller produced by QSI Industries of Portland, Oreg. This unit encodes separate key actuations of its user interface to automatically produce the required Severson polarity reversals. This is an improvement over manual switch actuation, but still does not solve the problem of consisting of non-decoder equipped locomotives, or the low control rate.
Severson in U.S. Pat. No. 5,773,939 shows a digital control method where an AC conventional control waveform has its alternating polarity cycles (which they term “lobes”) modified in expected polarity to encode a digital command sequence. This has the limitation set by the occurrence rate of the AC cycles, e.g. 120 Hz for US type power supplies, which is too slow for control of fast-changing functions and many locomotives on the layout.
Some systems such a the Hornby Zero-One encode a fast digital coding at fixed times (typically close to power cycle zero-crossings) within a low frequency power signal that is either sinusoidal or even a square wave. These methods also are limited, in that the fast digital encoding cannot occur essentially on-demand or effectively “at random” within the lower frequency power waveform.
Soundtraxx Inc., of Durango Colo., has demonstrated a DCC sound decoder that can automatically convert to operate on a conventional DC power control system and can vary e.g. steam chuffs in response to the DC track voltage and speed. A quick variation in DC control voltage can then be used to trigger e.g. a whistle sound on demand. This is useful to allow some limited DC control of functions (in this case, sound controls), but this is a very limited sub-set of the range of a dozen or more function actuated sounds and other functions available when a DCC command control system is used to control functions.
A further benefit of this new art is to employ power switching mechanisms and associated control and detection circuitry to perform integrated track occupancy detection in each separate track section that is improved over Ireland in U.S. Pat. No. 6,220,552 and further allow intelligent power management improved over the art of Ireland in U.S. Pat. No. 6,367,742.
The goal of all these technologies is to allow multiple locomotives in trains, or consists, to be freely formed with a mixture of different technology locomotives and permit some expansion of control and functions beyond just speed and direction and variation of prime mover sounds like diesel noise or steam chuffs in simple response to track power.
The provision of a control capability that allows expanded control over functions other than speed and direction, and the added implementation of power management and track occupancy detection without the aforementioned limitations of prior art, is a valuable addition to and improvement over the prior art of model railroad control.